Antagonism of moderate degrees of vecuronium-induced neuromuscular block by small doses of neostigmine.

We have studied the influence of a reduced dose of neostigmine on recovery from vecuronium-induced neuromuscular block in 26 adult patients, using electromyographic responses to train-of-four (TOF) stimulation. Neostigmine 10, 20 or 40 micrograms kg-1 was administered when the first response had recovered spontaneously to 5-10% or 40-50% of control. Antagonism was accepted as adequate when the first response reached 90% of control and the TOF ratio reached 0.7. At both degrees of spontaneous recovery, neostigmine 40 micrograms kg-1 evoked the most rapid antagonism. Clinical recovery was satisfactory with no differences between groups. Block produced by neostigmine was not observed. The pattern of recovery of the single response and the TOF ratio was not altered by neostigmine in the range of doses studied. We suggest that the dose of neostigmine should not be reduced below 40 micrograms kg-1 even when all responses of the TOF are present.